Muffler



Sept. 3, 1940. w. T. scARRlTT 2,213,614

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ATI'ORNEYS Sept. 3, 19,40.

W. T. SCARRITT MUFFLER l Filed May 18, 1939 2 .Sheets--Sheal 2 INVENTOR Wvdmjn TScariw ATTORNEYS Patented Sept. 3, 1940 UNITED STATES PATENT OFFICE IClaim.

'I'his invention relates to mumers for deadening the sound waves resulting from the explosions of internal combustion engines and the discharge o! the exhaust 'gases therefrom.

The invention provides a muiller which breaks up and deadens the explosive peaks of the sound waves by abruptly decreasing the velocity of the gases at the inlet and outlet ends of the muiiler by means of expansion chambers directly communicating with the inlet and outlet thereof and by providing intermediate the said chambers restricted passageways through which the gases pass at relatively greater velocity with a portion of the gases directed into attenuation chambers surrounding the restricted passageways. 'Ihe gases being retarded in their flow through the expansion chambers produce an interference of the peaks of succeeding explosions to thereby muiile or deaden the explosive peaks and produce attenuations oi!Y the sound wave which pass with the gases through the restricted passageways at high velocity and are caused to enter the' chambers surrounding the restricted passageways which conilne the gases therein and produce Whirls or streams which interact each other.

The invention further comprehends a muiller including an outer shell provided with end walls having inlet and outlet openings therein respectively, transverse partition walls separating the interior of the mullier into expansion and attenuation chambers, and longitudinally extending inner tubes carried by adjacent pairs of partitions and providing restricted passageways joining the expansion chambers at the ends thereof and having inwardly directed louvers for directing the gases from the passageways into the attenuation chambers between the partitions.

The invention further provides a muiller of the indicated character having partitioning units which subdivide the interior of the muiller into attenuation and expansion chambers, each of said partitioning units comprising a longitudinally extending duct constructed of sheet material which is rolled into tubular form with the longitudinal edges thereof disposed in abutting relation, and a pair of annular partition walls having ilanged inner and outer peripheries, the ends of the tubular duct being disposed within the inner ilanged peripheries thereof for holding the longitudinal edges of the sheet material in abutting relation and the duct in tubular formation, and one of said annular partition walls having an inwardly directed Irusto tubular terminal formed integrally with the inner anged with periphery projecting into the adjacent expansion chamber.

With the foregoing and other objects ln view, reference is now made to the following specification and the accompanying drawings illustrat- 5 ing the preferred form of the invention.

In the drawings: Fig. 1 is a longitudinal sectional view of a muiiler constructed in accordance with the invention. 10

Fig. 2 is an enlarged vertical sectional view taken approximately on the line 2-2 of Fig. 1.

Fig. 3 is a similar view taken approximately on the line 3 3 of Fig. 1.

Fig. 4 is an enlarged perspective view of one 15 of the muliler partitioning units.

Fig. 5 is an enlarged collective perspective view of the muffler partitioning unit showing the elements thereof in separated juxtaposition.

Referring to the drawings yby characters of 20 reference, the muiller includes an outer tubular shell I0 and end walls II and I2 secured to the shell at its opposite ends and which end walls areprovided with outwardly projecting aligned tubular collars I3 and I4 for connection respectively 25 with the exhaust and tail pipes of the motor vehicle.

In order to provide means for producing an interference of the sound waves of the eXplosions, a plurality of partitioning units I5 are 30 arranged in longitudinally spaced relation within the shell I U and with the endmost units spaced from the end walls II and I2 to provide within the shell expansion chambers A and B at the opposite ends thereof in direct communication 35 with the inlet and outlet openings I3 and I4 and intermediate expansion chambers C between the partitioning units I5. One of the units I5 is of relatively greater length than the other two as illustrated.

The partitioning units I5 each includes a 1ongitudinally extending duct indicated by the reference characters I6, IEa and I 6b respectively and a pair of annular partition walls I'I and I8 circumferentially secured upon the opposite ends of the ducts I6 to provide attenuation chambers D between the walls I'I and I8 and between the ducts and the shell I0 in surrounding relation with the ducts. The ducts are each constructed of a length of sheet material which is bent or rolled into tubular formation with the opposite longitudinal edges I9 and 20 Vthereof disposed in abutting relation.

Prior to the bending or rolling of the sheet into tubular formation, the same is transversely slitted at longitudinally and transversely spaced points and 'at one side of each of the slits the body of the sheet is offset to form inwardly oifset louvers 2| having forwardly directed openings 22 and inclined surfaces 23 for intercepting a portion of the exhaust gases passing through the ducts and directing the same into the attenuation chambers D.

The annular partition walls I1 and I8 are each provided with inner and outer circumferential anges 24 and 25 and in practice the walls are secured in position within the shell I0 by spot welding as at 8 or otherwise securing the anges 25 of either one orboth of the partition walls to the shell IB. The inner anges 24 of the partition Walls are telescopically tted over the opposite ends of the ducts and are spotwelded as at 9 or otherwise secured thereon to thereby retain the ducts in tubular formation and the longitudinal edges I9 and 20 of the sheet in abutting relation, while disposing the ducts in longitudinal alignment with each other and with the inlet and outlet openings I3 and I4. v

'I'he ducts I6 adjacent their ends are provided with outstruck circumferentially spaced lugs 26 providing shoulders against which the partition walls abut. The partition walls I8 are provided with'inwardly directed frusto-conical terminals 21 formed integrally with the flanges 24 and extending rearwardly therefrom in prolongation of the ducts While between the flanges 24 and 25 the partition Walls I8 are provided with rearwardly projecting radially arranged louvers 28 similar to the louvers 2 I.

In the embodiment illustrated, the muier is provided with three partitioning units I5 but the same may be of any desired number depending upon the length of the mufller required for a particular motor vehicle. A plurality of partitioning units I5 of varying length are preferably employed as it has been determined that the efliciency of the units I5 in blanketing sound waves of a particular pitch has definite relation with the length of the unit. In order, therefore, to provide means within the muilier which is effective for blanketing or deadenng the sound waves of different pitches, the foremost unit I5 is of relatively greater length than the two following units and the units are spaced apart within the muiller and from the end walls II and l2 thereof so that each unit may function to blanket the sound wave to which it is attuned in accordance with its particular length Without interference by the adjacent unit.

In operation the exhaust gases entering the chamber A through the restricted inlet I3 expand in said chamber with a consequent decrease in the velocity of the gases so that the sound waves of succeeding explosions are caused to interfere with each other within the said chamber to thereby produce a deadenlng or initial mufliing effect of the peaks of the explosion. The gases then enter the forward .end of the duct of the forev gases'in jet form into the expansion chamber C between the first and second units while the streams of gases emerging from the attenuation chamber D through the louvers 28 are directed radially inward causing interference with the gases emerging from the frusto-conical terminal 21 into the expansion chamber C. The gases from the expansion chamber C are then directed into the duct of the succeeding units I5 where the action is repeated, the vsucceeding umts being of a lesser length than the first unit, functions more effectively to blanket and muflie the sound waves of a diiferent pitch or length until the gases enter the final expansion chamber B from which they escape through the outlet.

It thus follows that there are alternate stages of decrease and increase in the velocity of the gases as the same pass successively through the expansion chambers and ducts, while a proportion of the gases is caused to travel through tortuous or sinuous paths where they alternately set up interference streams in the attenuation chambers and in the expansion chambers between the units and at the discharge end of the muffler.

What is claimed is:

A muiiier including an outer tubular shell having end walls provided with inlet and outlet openings, partitioning units including tubular ducts of different lengths disposed within said shell in .spaced relation with each other and with the end walls of the shell and aligned with said inlet amd outlet openings, and transverse partition walls surrounding the tubular ducts at the ends thereof and engaging the inner surface of the outer shell so as to divide the interior of the shell into attenuation chambers surrounding the tubular ducts and expansion chambers between the partitioning units and at the opposite ends of the shell in communication with said inlet and outlet openings, said tubular ducts having inwardly directed louvers for directing exhaust gases into the surrounding attenuation chambers, and the partition Wall adjacent the discharged end of each u nit having louvers for respectively directing exhaust gases from the attenuation chambers into the communicating expansion chambers.

WINI'HIROP T. SC 

